Download IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE)

IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE)
ISSN: 2278-1676Volume 3, Issue 3 (Nov. - Dce. 2012), PP 08-19
www.iosrjournals.org
Design Analysis of a 1.5kva Hybrid Power Supply for Power
Reliability
1
Ekpenyong, E.E, 2Bam, M.E and 3Anyasi, F.I
1,2,
Department of Electrical/Electronic Engineering, Cross River University of Technology, P.M.B 1123,
Calabar. Nigeria.
3
Department of Electrical and Electronics Engineering, Ambrose Alli University, P.M.B 14, Ekpoma, Edo State,
Nigeria.
Abstract: Interest involves a careful design of 1.5KVA hybrid power supply for power reliability. A renewable
single source system for a higher power demand application is often high in cost due to sizing of the source of
supply component to meat reliability requirements.
The system design is considered for the administrative office of the head of department, electrical and
electronics engineering in Cross River University of technology, Calabar, Nigeria.
The system operate at minimum running cost, population free environment, noiseless, reliable and
provide the convenient of a twenty-four hour power supply. With this system, energy efficiency is achieved by
lowering demand using demand response, incorporating temporary and permanent load shifting by back-up and
parallel mode respectively.
Keywords: Hybrid power supply, Power reliability, PV system, Inverter.
I.
Introduction
Power supply from the national grid is inefficient and unreliable, hence the need to provide alternative
source of power, [1]. Electrical power supply from renewable sources is advantageous as the increasing
Electrical demand is a scientific contribution to the peak demand on the grid. As individuals and companies
generate their power through renewable energy, the stress on the grid is reduced. However, there is an ongoing
interest in the possibility of making wider use of renewable energy, particularly in homes, offices and industries,
for the purpose of lighting, heating and powering of appliances. In most rural and sub-urban regions in Nigeria,
inhabitants do not have access to electricity supply. Where the Electrical energy is available, it is not reliable;
hence inhabitants resort to other forms of energy such as wood, paraffin, and diesel generators, which pollute
the environment and cause harm to man and plants [2].
Nigeria is endowed with abundant renewable energy resources, like biomass, wind, small and large
scale hydro with potential for hydrogen fuel, geothermal and ocean energies. Except for the large scale
hydropower generating station which serves as a major source of electricity, the current state of exploitation and
utilization of renewable energy resources in the country is very low[3]. The main constraint in the rapid
development and diffusion of technology for the exploitation and utilization of renewable energy resources in
the country is the absence of appropriate policy, regulatory and institutional framework to stimulate demand and
attract investors. The comparative low quality of the systems developed and the high initial upfront also
constitute barriers to the development of these systems.
The transmission network (that is from national grid) is overloaded with a wheeling capacity less than
4000MW. It has a poor voltage profile in most parts of the network, inadequate dispatch and control
infrastructure, radial and fragile grid network, frequent system collapse, exceedingly high transmission losses
[4]. It is a known fact that, Electric power availability enhances economic development of any society, while
non availability of power or power outage creates economic hardship. The power sector is unable to match
supply with demand of electric power and access to Electricity is low as about 60% of the population
(approximately 80 million people in Nigeria) are not served with Electricity [5]. Electric power sustains the
society in almost all ramifications; it becomes necessary for the Nigerian Government to sustain Electric power
availability to its citizenry. Electricity has never been adequate to the Nigerian populace, for 115 years now,
epileptic power supply and blackout is a regular phenomenon.
Solar energy is the energy transmitted from the sun in the form of electromagnetic radiation, which
requires no medium for transmission. Solar energy is the most promising of the renewable energy sources in
Nigeria, in view of its apparent unlimited potential. The sun radiates its energy at the rate of about 3.8 × 1023KW
per second. Most of this energy is transmitted as electromagnetic radiation which comes to about 1.5KW/M 2 at
the boundary of the atmosphere. After traversing the atmosphere, a square metric of the earth‟s surface can
receive as much as 1KW of solar power, averaging to about 0.5 over all hours of daylight. Studies relevant to
the availability of the solar energy resources in Nigeria have indicated its viability for practical use. Nigeria
www.iosrjournals.org
8 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
receives 5.08×1012KWh of energy per day from the sun and if solar energy appliances with 5% efficiency are
used to cover only 1% of the country‟s surface area then 2.54×106MWh of electrical energy can be obtained
from solar energy. The most common method of doing this is by the silicon solar cells. The amount of sunlight
that strikes the earth in one minute could supply the world‟s energy needs for an entire year. The solar resource
is so massive that it dwarfs every other resource on the planet. Grid-connected solar electric systems generate
electricity that can be used throughout a home, business or office, thereby, reducing the amount of electricity
needed to be purchase from the utility power company. When Photovoltaic power system generates more
electricity than needed for use, the excess is fed back into the electric grid and a credit is received from the
utility as the measuring meter reads backwards [6].
This work becomes necessary to demonstrate a Grid-connected solar power system for autonomous
generation of electric power showing its efficiency, low running cost, reliability, silent operation, pollution
free, minimal maintenance cost, automatic change-over system and an efficient payback system from the
inexhaustible and free supply of the sun. The optimization of the system is based on numerical analytical
modelling and the HOMER software package.
The quantity or amount of energy received from the sun depends on the positioning of the solar panel.
Typically, the solar modules are mounted on the roof of a building but our decision for mounting this project‟s
solar module on a stand-alone rack is to give room for further expansion as well as the renovation of the
workshop without the interruption of proper functioning of the system. A very important consideration is how
much sun the panel gets in the location chosen [6]. Solar cells loss efficiency in shaded locations, so the location
for mounting our module was where it gets full sunlight for most hours of the day. The panels were oriented to
the south-east to receive the maximum amount of sun [7]. The degree of tilt depends on the latitude at which
they are installed. Panels installed at 0 to 15 degrees latitude normally have a 15 degree tilt; panels installed at
15 to 25 degrees latitude should have a tilt that is the same as the latitude. For each additional five degrees of
latitude up to 40 degrees, an extra 5 degrees of tilt to the latitude is added. At latitudes of 40 degrees and above,
20 degrees of tilt is added latitude [8].
Solar power system captures the sun‟s energy with the help of photovoltaic (PV) cells in the solar
modules. These cells are connected together side by side in flat panels or modules mounted on a roof or open
area facing towards the sun. Energy from sunlight striking the top layer of the PV cells causes the cells to
release electrons. These electrons migrate through the electrical system and back to the cells again, causing a
DC electric current in the system, the same type of current produced by a battery. A device called an inverter
converts the current from DC to AC to match the kind of current running through a standard electric outlet [9].
On cloudy days or when there is no sunshine, solar power system still produces electricity, although in lesser
quantity, on this note, electricity is drawn from the battery bank to meet the energy needs in times of bad
weather.
II.
Materials And Method
PV Systems
Photovoltaic systems vary in complexity and depend basically on the total load demand and the
availability of sunlight. The estimation here is based on hybrid principles rather than stand-alone. The major
components in this system are; PV array, charge controller, inverter, battery bank, utility feeder and installation
accessories. See Figure 1.
Figure1: Basic photovoltaic system integrated with grid
Source: Non- Conventional Energy Source (G.D. Rai) 2008
III.
Pv Cell Arrangements
PV cells are connected in parallel to achieve the desired current and in parallel to achieve the desired
voltage. The optimum operating voltage of a photovoltaic cell is generally about 0.45V at normal temperatures,
and the current in full sunlight may be taken to be 270A/m 2 [9]. A decrease or increase in the solar radiation has
little effect on the voltage, but the current and power are decreased or increased proportionately. By combining a
www.iosrjournals.org
9 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
number of solar cells in series, the voltage is increased but the current is unchanged. However, to increase the
current output at the same time, several strings would be connected in parallel as depicted in the Figure 2.
Consequently, if a single cell in a string should fail, the whole string would become inoperative. The cells in the
remaining strings would maintain the voltage, but the current and power output of the system would be
decreased by the loss of one string of cells. A short circuit in a cell would not disable the string, although there
would be a slight drop in voltage. This danger could be eliminated by including a diode, which permits current
flow in one direction only, at the end of each string. Alternatively, rather than have a number of strings of cells
in parallel, the current and power could be increased by locating a single string of cells at the focal line of a sun
tracking, parabolic trough, concentrating collector. These results in decrease in voltage because of the inevitable
higher temperature of the solar cells material, but the current would increase approximately in proportion to the
concentration factor of the collector [9].
TERMIN
TERMINA
AL
L
Figure.2: PV cell arrangement in series and parallel
Source: Non- Conventional Energy Source (G.D. Rai) 2008
Stand-alone PV systems: An off grid stand alone solar PV system is independent of the utility grid. Electricity
from a stand-alone system is only used at the site of installation. The generated power stored in batteries is used
as needed. A typical off grid house using a solar PV system is usually rated at 3 kilowatt (KW) is 15 – Kwh/day
and provides power only for essential devices [10]. An off grid or stand alone PV system is independent on the
commercial utility power, Electricity from an off grid system is only used at the installation. The generated
power is stored in battery and used as needed. The advantage of an off grid system have freedom from the
commercial utility system and in the long run lower electrical cost.These disadvantages are limitations on power
consumption which is dependent on the capacity of the battery bank to supply electrical power during bad
weather days and being self sufficient on power.
Loads: Most common loads are 12V, 24V, 36V, 48V, DC appliances or 220V AC appliances. The estimated
power consumption is given in intervals of hours or minutes, for the length of a week, month or year. If both a
DC and AC system bus exist, some of the DC bus energy can be routed through the inverter to the AC loads.
The loads can posses‟ different priorities in terms of when they need to be met by the electricity supplied. There
are optional loads which can either be supplied at the specified time instant but do not have to, and then they are
suitable as dump loads. There are deferrable loads, which do not have to be supplied at the specified time
instant, but need to be covered within a certain time interval. Other high priority loads need to be run at the
given time instant. These loads include 5 fluorescent points, 2 ceiling fans, 5 laptops, two 14” television and 1
satellite decoder [11].
Table 1 shows a typical appliances power rating, why Table 2 shows the load estimate.
Table 1: Typical Appliances Power Rating
APPLIANCE NAME
Air conditioner
Ceiling fan
Desktop computer
Food mixer or blender
Heater
Iron
Lighting kitchen
Lighting out-door
Lighting office
Microwave
POWER (WATTS)
1350
75
360
110
1500
1100
250
150
150
1450
www.iosrjournals.org
10 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
Radio-stereo
Oven
Refrigerator (frost-free)
Toaster
Vacuum cleaner
Water heater (electric)
Television
Deep freezer
Laptop
Printer
Satellite dish
VCR
Kettle
Mobile phone charger
Fluorescent lamp
110
5000
445
1100
700
3200
200
500
75
100
30
40
2500
15
40
Table 2: Load estimate.
QUANTITY POWER
HOURLY
RATING
USE (h)
(W)
5
40
6
TOTAL
POWER
(W)
200
ENERGY
(W)
2
3
FLOURESCENT
LAMP
FANS
LAPTOPS
2
5
100
65
6
6
200
325
1200
1950
4
14” TELEVISION
2
62
6
124
744
5
SATELLITE
DECODER
SPARE
1
100
6
100
600
250
1199
250
5944
S/N
APPLIANCE
1
6
1200
Total power becomes 1199watts
Total power in KVA becomes 1199 /0.8
= 1.498KVA
=1.5KVA. This matches with the inverter size.
Energy in watt-hour =5944Wh
Energy in kilowatt/hour = 5.9Kh
IV.
PV System Design (PV Sizing)
Due to the variable nature of the energy source, one of the most expensive aspects of a PV power
system is the necessity to build system autonomy to provide reliable power during periods of adverse weather or
increased demands. This is accomplished by over-sizing the PV array and enlarging the battery storage, which
are the two most costly system components. Improved system usage and operation may be more easily achieved
with a hybrid system than with a single-source application [12]. Hybridising a PV system often reduces the need
for over-sizing the PV array to achieve system autonomy especially when complementarily different energy
sources can be used effectively. Photovoltaic systems here are combined with battery bank and utility supply to
cope with higher energy demands or in weather by extended periods of little sunshine to form the hybrid
systems. The PV sizing variables to be optimized are the size of a PV panel and the number of strings in a PV
array. A photovoltaic module model based on the electrical characteristics provided by the manufacturer is
considered. The model calculates the power produced by a solar module using the photo conversion efficiency
formulas as shown in Equations below [12].
η = PSTC / EIN
. . . . (1)
Pout    Ei  C f
. . . (2)
Where:
www.iosrjournals.org
11 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
 = Photo conversion efficiency
PSTC = Power at 25 C and 1000W / m 2
2
EiN 
Standard Test Condition (STC)
1000W / m
Pout = Power Output
2
Ei  Effective solar irradiation impinging the cell in W / m
C f = Correction factor for 
This method is quicker and only needs the power produced by the PV module at 1000 W/m² and the
irradiance level reaching the module. The method assumes that the efficiency of the solar module is constant at
any irradiance level global solar radiation of Calabar (Latitude 4.970N, longitude 88.350E and altitude 6.14m
above sea level) [13]. Global solar radiation data measured in KWHm-2day-1 can be converted to MJm-2day-1
using a conversion factor of factor of 3.6 [14].
Figure 3: Map of the Project Area.
Source: BritanniaEncyclopaedia
In this work, the aim isto calculatingthe number of modules needed to supply a load of 1.5KW in the
H.O.D‟s office, Department of Electrical and Electronic Engineering, Cross River University of Technology in
the city of Calabar. The solar radiation during the month of January in Calabar is 14.1300 MJ -2m2[32] and
average sunlight hours of 4 hours [13]. The map of studied area is shown in Figure 3.
The solar radiation per hour considering 4 hours is (14.1300 MJ-2m2) / (4h) = 981.25W/m² per hour.
Using equation (1), the number of solar modules needed by the system using quick method can be calculated
[4].
Photo conversion efficiency is calculated by

PSTC
EiN = 110 = 0.11
1000
Now using equation (2), Power can be calculated thus;
Pout    Ei  C f
= (0.11)*(981.25)*(0.95)
= 102.5W.
Now, to calculate the number of solar modules needed for the system using the quick method, we take the load
power of 1498W and divide it by the power generated from the solar module (1500W)/(102.5) = 14.6.
Meaning, 15 PV module Pss 12110 simba solar module which is equivalent to 1,650watts PV is adequate to
generate enough power to supply this load of 1.498 (1.5KVA) [13].
www.iosrjournals.org
12 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
V.
Batteries In A Hybrid System
Typically, battery efficiency is 80% requiring a battery bank capacity greater than what is actually
needed [7]. Batteries periodically need servicing and have the highest potential offaults in a solar PV system.
The important specifications to consider for selecting a battery are:
Capacity 6V dc, 350 Amp hour, 350 Amp/hour 20 hour Rate and 460 Amp/hour 100 hour rate.
Some basic steps to ensure good condition of your battery would be:
 Fully charge your battery before use.
 Be sure to fully tighten the connectors and properly wire the cables.
 Fasten vent caps tightly and check from time to time.
 Batteries should be wiped free of all corrosion, dust, and dirt frequently.
VI.
Modelling Of The Battery Bank
The system batteries are connected in parallel. Positive terminals are connected to positive terminals
and negative terminals to negative terminals. Parallel connections are established by mutually linking the “free”
positive terminals of the “series rows” on one side, and mutually linking the “free” negative terminals on the
other side [15]. The number of rows to be linked in parallel depends on the number of parallel connections to be
Established by the connections. See Figure 4.
Figure 4: Parallel Connection
One set of wires – positive and negative – is connected to the charge controller (incoming current), and
one set to the inverter (outgoing current) [15].The positive wires (incoming and outgoing) and the negative wire
(incoming and outgoing) are best connected to diagonally opposite corners in order to equalize the
charge/discharge level of the batteries (which will positively affect the sun times and battery life). The model
produces a high current capacity as compared to a unit battery which is 12V, 200Ah. Thus by this configuration,
the system rating becomes 24V, 400Ah. See Figure 5.
Figure .5: Showing Incoming and outgoing current
VII.
Battery Sizing
Battery sizing consists in calculating the number of batteries needed for a renewable energy system.
This mainly depends on the days of autonomy desired. Days of autonomy are the number of days a battery
system will supply a given load without being recharged by a PV array, utility supply or another source. If the
load being supplied is not critical then 2 to 3 autonomy days are commonly used. For critical loads 5 days of
autonomy are recommended [16]. A critical load is a load that must be used all the time. The battery‟s capacity
will decrease at lower temperatures and increase at higher temperature. The battery‟s life increases at lower
www.iosrjournals.org
13 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
temperature and decreases at higher temperature. It is recommended to keep the battery‟s storage system at 25
ºC. At 25 ºC the derate factor is one [11].
The following procedure shows how to calculate the number of batteries needed for a hybrid energy
system. Equation (3) shows how to calculate the required battery bank capacity for a hybrid renewable energy
system [16].
BR 
L Ah / Day  DST
. . . (3)
M DD  D f
Where L Ah / Day is the Amp-hour consumed by the load in a day (Ah/Day)
DST is the number of autonomy days
M DD is the maximum depth of discharge
D f is the derate factor
BR the required battery bank capacity in (Ah).
Equation (4) presents how to calculate the number of batteries to be connected in parallel to reach the Amp
hours required by the system.
BR
. . . (4)
BC
Where B R is the required battery bank capacity in (Ah).
BP 
BC is the capacity of the selected battery in (Ah)
BP is the number of batteries that needs to be in parallel.
Equation (5) presents how to calculate the number of batteries to be connected in series to reach the voltage
required by the system.
BS 
VN
VB
. . . (5)
Where V N is the DC system voltage (Volt)
V B is the battery voltage (Volt)
B S is the number of battery that needs to be in series.
The total number of batteries needed is obtained by multiplying the total number of batteries in series and the
total number of batteries in parallel as shown in equation (6).
. . . (.6)
N B  BS  BP
Where,
B S is the number of batteries in Series.
BP is the number of batteries in parallel.
N B is the total number of batteries needed.
In this work, we sized a battery system that will supply 1498W per day to a AC electrical load. The DC voltage
of the battery system will be 24V. The number of autonomy days will be 4 days. The maximum depth of
discharge will be 50%. The batteries are kept at a temperature of 25ºC, thus, the derate factor is 1. We choose
deep cycle Acid Battery models. It has 200Ah at 12Volts. The Amp-hour load of the system, take 1498Wh/day
and divide it by 24V, is 49.9Ah/day. Then using equation (3) to (6), we calculate the batteries required by this
system.
Required Battery Capacity BR 
L Ah / Day  DST
M DD  D f
= [(49.9)*4]/ (0.5 *1)
= 399.2Ah
≡ 400Ah
Batteries in Parallel B P

BR
= [(399.2)/200] =1.99 = 2
BC
www.iosrjournals.org
14 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
Batteries in Series BS

VN
= 24/12= 2
VB
Total Number of Batteries N B  BS  BP = 2*2 = 4
VIII.
The Inverter
An inverter is an electrical device that converts DC to AC. The converted AC could be at any required
voltage and frequency with the use of appropriate transformers, switching and control circuits [11]. Inverter in
this work is used to supply AC power from DC solar panels and batteries. The Grid tie inverter can feed energy
back into the distribution network because it produce alternating current with the same wave shape and
frequency as supplied by the distribution system and can also turn on the hybrid system automatically in the
case when utility supply switches off.The electrical inverter is a high-power electronic oscillator. It is so named
because early mechanical AC to DC converters was made to work in reverse, and thus was "inverted", to
convert DC to AC.The inverter performs the opposite function of a rectifier. The electricity can then be used to
operate AC equipment like the ones that are plugged in to most house hold electrical outlets. The normal output
AC waveform of an inverter is a sine wave with a frequency of 60Hz. The efficiency of converting the direct
current to alternative current of most inverters today is 90 percent or more. Many inverters claim to have higher
efficiencies but for this project the efficiency used is 90%. [9] The inverter has output voltage of 220V and
produces a sine wave AC output signal of 60Hz [17].
A Sine wave inverter produces voltage with low total harmonic distortion (normally below 3%). It is
the most expensive type, which is used when there is a need for clean sinusoidal output for some sensitive
devices such as medical equipment, laser printers, stereo, etc. sine wave inverters put out a wave that is the same
as that you get from the power company. Often times it is even better and cleaner. Sine wav inverters can run
anything, but are also more expensive than other types. One solution to the problem of a few small appliance not
working well with modified sine wave inverters is to get a large wattage of modify inverter. This gives more
tolerance, and allows it to give better efficiency powered up without having to run the larger inverter to full
capacity. This is the advantage of pure sine wave inverter over other type of inverters.
There are a number of topologies used in the power inverter circuits. Cheap square wave circuits
suitably primarily for this kind of work may also use a push-pull converter with a step-up transformer. Most
commercially manufactured models use the same basic multi-stage concept; first a switching pre-regulator
(SMPS) steps up a voltage from an input source to a DC voltage corresponding to the peak value of the desired
AC voltage. The output stage generates an AC. This stage usually uses a full-bridge configuration. If a half
bridge is used, the DC-link voltage should be at least twice the peak of the generated output voltage. Input to
output galvanic isolation is provided by either a high-frequency transformer in the SMPS switching preregulator, or by a large low-frequency output transformer [8]. If a low-frequency transformer is used, the
sinusoidal voltage is generated on its primary side and transformed to the secondary side. The output voltage
level can be controlled either in square-wave mode or in pulse width-modulated (PWM) mode. Sine wave
circuits use PWM mode, in which the output voltage and frequency are controlled by varying the duty cycle of
the high frequency pulses. Chopped signal then passes through a low pass LC-filter to supply a clean sinusoidal
output. [18]. See Figure 6.
Figure 6: Block diagram of an inverter system
Analytical Method
This method can be used to select the correct size of the resistor that is suitable to produce 50Hz
frequency. Using the formula,
F = 0.22/RC
Where,
F = 50Hz (PHCN)
C = 0.1× 10-6 F
50 = (0.22 × 10-6 F)/ 0.1 × R
5R = 0.22 × 10-6
www.iosrjournals.org
15 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
R = (0.22 × 10-6)/ 5
R = 44000
R = 44KΩ
Hence sending switching with variable resistor size of 50KΩ and 0.1× 10 -6 F capacitor, frequency switching of
50Hz is guaranteed [19].
Operation of 1.5KVA (24/220V) single phase inverter
When the switch S1 is switched ON, the current is passed from 400Ah deep cycle battery of 24V to the
voltage regulator and the regulator 7805IC generate 5V to the oscillator IC4047, this oscillator is an
astablemultivibrator which gives out the square wave – signal at pin 10 and 11 [20]. This oscillation is adjusted
to frequency of 50Hz using the expression F = 0.22/RC, by vibration of 50KΩ variable resistor about 46KΩ, the
oscillation of 50Hz is released to trigger the base current to flow to the transistor (PREAMP), the transistor
switches at this frequency when there is base current that is limited by 100Ω resistor, this signal from emitter
terminal of the transistor is amplified and drive the gate of MOSFET(IRFZ150)which switches the 24V in
secondary winding of centre tap transformer at 50Hz frequency and the output voltage is 220V at primary of the
transformer which depend on turn ratio of transformer V1/V2 = N1/N2.[20]. See Figure 7 for the complete
diagram of the 1.5KVA inverter system.
24V
Battery
IRFZ1
D1
50
LM781 +12V
2
O/
V.R 50k
P
2
1
10Ω
0.1u
F
8 14
6
011
1 4 9 12
220
220V
2N222
Ω
220
1k
Ω
2N222
10
24V
Ω
D1
IRFZ1
50
24V/220V
Transforme
r
Ω
Battery
Figure 7: Circuit diagram of 1.5KVA inverter using IC CD4047 +IRFZ150
The inverter system gives out an output of steady AC voltage which makes it suitable to be used in
powering sensitive electronics (equipment) like the ones used in this project. This inverter uses 3 – stage
chargers, so it can be left powered up all the time because of the inbuilt power relay. Meaning that, when
running from AC, the power feeds through an inverter, at the same time, some power is being tapped for the
battery charger. If the AC power goes out, the inverter automatically switches to battery power. In most cases it
is difficult to notice it but for a light flicker, it is so fast because of the two transistor analogy of a thyristor
which is part of the circuit. This system is designed to work automatically, it does not require anyone to be
employed to physically turn it ON/OFF before it can charge the battery and at the same time, when required;
supplies current to the appliances.
Inverter Design
The solar inverter is a critical component of an entire solar energy system. It performs the conversion
of the variable DC output of the PV cells into a clean sinusoidal 50Hz [11] current suitable for supplying the
commercial electrical grid or local electrical network.Inverters are usually sized according to the maximum
required continuous power output. Most inverters are capable of handling three to six times more power than
their rated size for short periods of time in order to accommodate surge currents which occur when starting a
motor.An inverter needs to be sized to cover peak or non-surge peak load [11].
Sizing of the inverter in hybrid power supply system
Inverter sizing consists in calculating the number of inverters needed for the PV system. In small
hybrid systems such as these, one inverter is enough to supply the power but for a larger hybrid system more
www.iosrjournals.org
16 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
inverters may be needed. When you select an inverter you must have a DC voltage equal to your inverter DC
voltage and have an AC voltage and frequency equal to your home and utility values [12].
Equation (7) shows how to calculate the number of inverters needed for a stand- alone hybrid system [12].
Number of Inverters required 
PLOAD
PINVERTER
. . . (7)
Where PLOAD represent the maximum continues power load your System consumes. PINVERTER is the maximum
power that can be supplied by the inverter.
In this project, the number of inverters needed for the energy system that have an AC load of 1498W is
calculated. We have to select an inverter with an output power of 1199W or more. The inverter model used has
an output of 1500W at 220V. Using equation (7): [12]
Number of Inverters required 
PLOAD
PINVERTER = 1498/1500 = 0.99 =1
The total number of inverters needed is one.
Over Voltage Regulator
The overall operation of the voltage regulator will be discussed as follows.
Power supply
Amplifier
Relay
Astablemult
circuit
switch
ivibrator
Load
Figure 8: System’s blockcircuit
diagram
The Power Supply Unit (PSU)
𝑉𝑜𝑢𝑡
= 𝑅𝐿
𝐼
. . . (8)
Where,
𝑉𝑜𝑢𝑡 = 30𝑉 𝑎𝑛𝑑 𝐼𝑐 = 3𝐴
The value of RL will then be
𝑉𝑜𝑢𝑡 = 𝑅𝐿 𝑋 𝐼𝑐
. . . (9)
𝑐
𝑅=
Filtering Capacity Calculation
1
𝐶𝑓 = 2
2×𝐾×𝐹×𝑅𝑙
30
= 10Ω
3
. . . (10)
Fr = Ripple frequency
K = Ripple factor
RL = Load Resistance
It should be noted that:
Fr = 100Hz (According to GB standard F = 50Hz × 2)
K = R. M. S. Ripple voltage/ DC output voltage
RL =20 to 100Ω
Chosen value
Fr = 100Hz
R.M.S ripple voltage = transfer current rating × RL
= 500Mv
Therefore,
www.iosrjournals.org
17 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
𝑘 = 50 ×
𝐶𝑓 =
10−3
10
= 50 × 10−2
1
2
2.100 × 50 × 10−3 × 20
= 3300𝜇𝑓 (𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒 𝑣𝑎𝑙𝑢𝑒)
Design Equation of an AstableMultivibrator (AMV)
𝐹 = 1.44(𝑅𝐴 + 2𝑅𝐵 )𝐶𝑡
Where,
RA =Astable resistor
RB = Biasing resistor
Cf =Timming capacitor
F = frequency of oscillation
. . . (11)
IC 7805 Voltage Regulator
In the alternative, IC 7805 can be used for voltage regulation.The IC 7805 is basically used in this
project for the voltage regulation. This IC provides a fixed positive output voltage. Although, many types of IC
regulators are available, the 7800 series of IC regulators is the most popular. The last two digits in the part
number indicate the DC output voltage. For example, from the data table below, the 7812 is a +12V regulator
whereas the 7805 is a +5V regulator. This 7800 series provides fixed regulated voltages from +5V to +24V as
shown in Table 3, [20].
Table3: The 7800 seriestable
TYPE
OUTPUT
NUMBER VOLTAGE
7805
+5.0V
7806
+6.0V
7808
+8.0V
7809
+9.0V
7812
+12.0V
7815
+15.0V
7818
+18.0V
7824
+24.0V
Source: V.K. Metha&RohitMetha, „Principles of Electronics‟. 2008.
Integrated circuits (IC) are preferred for voltage regulator because properties like thermal
compensation, short circuit, protection and surge protection can be built into the device.
IX.
Conclusion
The system designed is to be used in conjunction with the electrical system of the office facility for use
during the day or day light hour and when grid power is down. It can also work the other way, when the solar
PV does not produce enough electricity, it can draw power from the grid. This is done automatically through a
device that monitors the available power and switches between PV and grid power. The design of hybrid system
is more complicated and expensive, but they are the most effective in providing constant and reliable electricity.
The grid tie inverter feed energy back into the distribution network because it produces alternating current with
the same wave shape and frequency as supplied by the distribution system and can also turn on the hybrid
system automatically in the case of power failure. The aim of this work was to demonstrate that Hybridization of
various renewable energy sources and battery bank is a key for system cost effectiveness and high performance
than any other variant based on a single renewable source. The sizing results suggests that HOMER softwareis a
powerful, efficient and flexible tool that gives the optimum and cost effective systems based on renewable
source.
www.iosrjournals.org
18 | Page
Design Analysis Of A 1.5kva Hybrid Power Supply For Power Reliability
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
Akpama, E.J.,”Designing a photovoltaic sustained sector: a review of current practice,”domestic use of energy conference, pp 155160. 2011.
M. Marvwan& H. ImadIbrik, “Techno- economic feasibility of energy supply of remotevillages as Palestine by PV- systems, diesel
generators and electric grid,” renewable andsustainable energy. Reviews pp 128-138, 2006.
Sambo, A.S., International centre of energy, “Energy and Development Report, Renewable Electricity Action Program,” federal
ministry of power and steel, Nigeria 2006.
Augustine C. &Nnabuchi M. N. “Relationship between Global Radiation And Sunshine Hours ForCalabar, Port Harcourt And
Enugu, Nigeria.” International Journal of physical sciences vol. 4(4), pp.182-188, 2009.
Chimeka I. U, &chineke T. C. “Evaluating The Global Solar Energy Potential AtUturu,
Nigeria.”International journal of
physical sciences.Vol.4(3), pp 115-119, 2011.
Dusabe, J.L. Munda, &Jimoh A.A. “Small Scale Solar Energy System in Rwanda: Status. And Sustainability.”Domestic use of
energy conference, pp 137-141, 2009.
Rogers A. Messenger, “photovoltaic” floridaatlantic university, 2006.
Retrieved from “ http://en.wikipedia.org/wiki/portal:Renewableenergy.”
G.D. Rai, “non-conventional energy sources.”Khannapublishers 2-B, Nath market, NaiSarak Delhi-m110006. India.2008.
Donald E.O. & David E.C., “Utility Grid-Connected Distributed Power Systems.”National solar energy conference.ASES solar,
1996.
Gabrielle Seeling-Hochmuth, “Optimisation of Hybrid Energy Systems Sizing and Operation Control.” 1998.
Ani, V.A. &Nzeako A.N.,” Energy Optimization at GSM Base Station Sites Located inRural Areas,” international journal of energy
optimization and engineering (IJEOE), 2011.
Augustine C. &Nnabuchi M. N. “Relationship between Global Radiation And. Sunshine Hours ForCalabar, Port Harcourt And
Enugu, Nigeria.” International Journal of physical sciences vol. 4(4), pp.182-188, 2009.
Sabbert C., &Seeling-Hochmuth G. “Review of hybrid energy system design andperformance. “EDRC, University of Cape Town,
1997.
[PVDI] solar energy international.”Photovoltaic Design and Installation Manual,”New Society Publishers, 2007.
Patel M.,”Wind and Solar Power Systems,” second edition, Taylor& FrancisGroup, 2006.
Igbal M.,“An Introduction to Solar Radiation.”Academy press. New York, pp. 6-51 1983.
Peter Lilienthal, Tom Lambert etal, National Renewable energy laboratory.“Getting Started Guide For HOMER Version 2.1”. 2005.
Sandia, “Stand-Alone Photovoltaic Systems.” A Handbook of Recommended Design Practices.Sandia National Laboratories. 1994
Paul Breeze, “Power generation technologies.” 2005
Semiconductor components, function IC CD4047 Datasheet, http://www.functionic cd 4047. 2012.
Fairchild semiconductor, “FQP17N40Datasheet,”http://www.fairchildsemi.com/ds/fq/fqp17N40.pdf.2012
V.K. Metha&Metha.“Principles of electronics”s.chad technical,2007.
http://www.biomassenergycentre.org.uk/portals/page.
www.iosrjournals.org
19 | Page